Microminiature refrigerators of the type illustrated in the aforementioned patents essentially comprise a laminated assembly having micron-sized fluid passages formed in outer plates of glass or the like separated from each other by an intermediate layer. Heat conduction requirements for such intermediate layer are essentially conflicting in that it must have high conductivity across its thickness to facilitate heat exchange between inlet and outlet fluid passages, but must have low conductivity lengthwise to facilitate maintenance of one end at cryogenic temperatures. It is a general object of the present invention to provide an improved intermediate layer having enhanced heat conductivity across its thickness while maintaining high lengthwise insulation capacity.
Another object of the invention is to provide a microminiature refrigerator of the desired type in which heat exchange characteristics of the intermediate layer are specifically adapted to the design operating temperature of the refrigerator.